An expression statement computes an expression, such as a function call or assignment. The expression result is discarded, so the expression is typically evaluated for its side effects. (See Chapter 3 for details about expressions.) The statement syntax is simply an optional expression followed by a semicolon:
A statement with no expression is called a null statement. Null statements are most often used for loops when no code is needed in the loop body.
Here are several examples of expression statements:
42; // Valid but pointless cout << 42; // More typical x = y * z; // Remember that assignment is an expression ; // Null statement